Lezen-Gzecka, Tetani Vigilante

Vigilance, Lifelink, Double strike
When Lezen-Gzecka, Tetani Vigilante enters the battlefield, you may pay {x}.
Whenever an opponent casts a spell with converted mana cost {x}, you win the game.
Legends speak of an ancient warrior destined to save Tetani from a threat older than time itself.